As a bearing device to be used for a liquid fuel turbopump of a rocket engine in a low-temperature, high-speed rotation environment and a rolling bearing device to be used for a space apparatus in a vacuum environment, a double row angular contact ball bearing is used in some cases. In this bearing device, angular contact ball bearings are arranged in two rows on an outer peripheral surface of a main shaft serving as a rotation shaft, and in many cases, an inner race spacer and an outer race spacer are mounted between the double row angular contact ball bearings to perform axial positioning of inner races and outer races.
In the above-mentioned rolling bearing device to be used in a low-temperature, high-speed rotation environment or in a vacuum environment, due to a problem of grease evaporation or the like, grease lubrication cannot be employed. On the other hand, there is an increasing demand of the market for improvement in reliability (safety factor) of this type of bearing device as a product through increase in life of the bearing device. Therefore, it is necessary to increase an absolute amount of a lubricant that contributes to the lubrication at the time of bearing rotation. In view of this, in a case of the rolling bearing device in which the grease lubrication cannot be employed, the absolute amount of the lubricant is increased through the following oil lubrication or solid lubrication.
In the former case of oil lubrication, the rolling bearing device includes, for example, an oil sump portion for storing lubricating oil in the inner race spacer. At the time of bearing rotation, the lubricating oil stored in the oil sump portion is scattered to the inner race side by a centrifugal force, and is supplied to an interior of the bearing between the inner race and the outer race (see Patent Literature 1). In the latter case of solid lubrication, the rolling bearing device includes, for example, columnar rolling element spacers each made of a material having self-lubricity and arranged between adjacent rolling elements among a plurality of rolling elements arrayed between the inner race and the outer race. At the time of bearing rotation, lubricating powder is scattered by friction from surfaces of the rolling element spacers that are held in contact with the rolling elements, and is supplied to the interior of the bearing (see Patent Literature 2).